The present invention relates to a method and circuit for reducing microphony in a circuit having ceramic surface-mounted capacitors.
In recent years, the use of surface-mounted components in electronic circuits has become more common. Although the surface mounting construction has advantages, the ceramic surface-mounted capacitors are subject to interference voltages caused by microphony. Such microphony is especially detrimental in filter circuits of radio telephones and in voltage-controlled oscillator.
Microphony of a ceramic capacitor means that the voltage between the capacitor terminals changes under mechanical action. Such as impacts or vibration, which cause the capacitor to deform. Portable and car mounted radio telephones are susceptible to this phenomenon. Attempts have been made to reduce microphony by locating the critical capacitors they are the most firmly fastened, i.e., where their deformation is minimal. Special attention must also be paid fastening the surface-mounted capacitor to the printed circuit board.
This approach produces problems in circuit design because ti substantially restricts the components' location and/or increases the costs of mechanical installations.